An 18-year-old student was arrested after a journal was found detailing plans to shoot his classmates at ACES High School in Washington.

According to the Everett Police Department in Washington state, the 18-year-old’s grandmother called 911 Tuesday morning after finding the journal and believed the threats to shoot students at the school were believable.

Officers responded to the house and were shown excerpts of the journal and were told the grandson had a semiautomatic rifle stored in a guitar case. As officers reviewed the journal, they were alarmed by the statements and detailed plans to shoot students and use homemade explosives, according to a press release.

Excerpts from the journal show the teen had been thinking about the shooting frequently and wanted to make it “infamous,” according to probable cause documents.

Court documents state the young man wrote, “I can’t wait to walk into class and blow all those (expletives) away,” and “I need to make this shooting/bombing infamous. I need to get the biggest fatality number I possible can.”

Prosecutors allege the suspect had inert grenades in his bedroom that he planned to fill with black powder along with the AK-47 hidden in a guitar case.

The student attended Kamiak High School last year before transferring to ACES Alternative School this fall. Detective say he simply flipped a coin to determine which school to target. It came up ACES.

ACES High School was contacted and told about the threat. The student was arrested at the school, and a knife and marijuana were found on his person.

This occurred the same morning that the 17 children were tragically shot and killed while dozens more was injured at a South Florida high school.